8
www.fairchildsemi.com
FAN8024ED Rev. 1.0.0
F
Application Information
1. Reference Input
& and
Stand-by Function
Reference input (PIN 27)
The applied voltage at the reference input pin must be between 0.8V and 6.5V
,
when V
CC
=8.5V.
Stand-by input (PIN 28)
The following input conditions must be satisfied for the stand-by function.
2. Protection Function
Thermal shutdown (TSD)
If the chip temperature rises above 175
°
C, the thermal shutdown (TSD) circuit is activated and the output circuit enters the mute
state, which is off state. The TSD circuit has a temperature hysteresis of 25
°
C
.
3. Separation of Power Supply
PV
CC1
(PIN 9)
PV
CC1
is the power supply for the loading driver. The range is between 5V~12V.
PV
CC2
(PIN 21)
PV
CC2
is the power supply for the actuator drivers that include focus and tracking actuators. The range is between 5V~12V
V
CC
(PIN 8)
VCC pin supplies power for the sled driver and the signal logic part. VCC
≥
PVCC1(PVCC2)
.
4. Current feedback channels (channel 1
& and
4)
The reference voltage(ref) is supplied externally through pin 27.
The input OP-amp output signal is amplified by (20K/10K) times and then fed to the current feedback amplifier.
The current feedback amplifier compares the output current sensed input and command input and then makes the controlled out-
put to eliminate delay effect of the load. Please refer to the Application Note 4109 for additional information about current feedback
theory (http://www.fairchildsemi.com/an/AN/AN-4109.pdf).
The DC gain of current feedback amplifier and power amplifier is unity, which
is 1 [A/V]. Users can change the gain by adding
external resistor at the command input.
Stand-by input voltage
OPERATION
Below 0.5V or open
The stand-by function is activated so the bias block and
power block are disabled
Above 2.0V
Recover the normal operation
L
X2
20k
10k
7.5k
7.5k
ref
actuator
Sensing resistor
Rext
Cext
Command
power amp
current feedback amp